Zwitterionic surfactant as well as preparation method and application thereof

Abstract

The invention relates to the technical field of surfactants, and provides a zwitterionic surfactant as well as a preparation method and application thereof. The surfactant is shown as a formula (I), wherein in the formula (I), R1 is selected from C4-C30 alkyl; r2 is selected from H and C1-C10 alkyl groups; r3 is selected from H, methyl and ethyl; r4 is selected from H and C1-C4 alkyl; m1 and m2 are respectively and independently selected from any integer between 0 and 50, and m1 + m2 = 1-50; the structure of R5 is shown as-(CH2) n1 (CH (OH)) n2 (CH2) n3SO3 (M) n, n1 is any integer selected from 1-4, n2 is selected from 0 or 1, n3 is any integer selected from 1-4, n1 + n2 + n3 is less than or equal to 6, M comprises at least one of alkali metal ions and alkaline earth metal ions, when M is the alkali metal ions, n is 1, and when M is the alkaline earth metal ions, n is 0.5; xi-is an anion, wherein i is the number of charges of the anion. The zwitterionic surfactant provided by the invention has the advantages of being good in temperature resistance and salt tolerance, high in interfacial activity and capable of effectively reducing the water injection pressure of the low-permeability reservoir, can be used in enhanced oil extraction production for reducing pressure and increasing injection of the low-permeability reservoir, and can obviously improve the recovery efficiency of the low-permeability reservoir.

Description

Technical Field

[0001] This invention relates to the field of surfactant technology, and more specifically, to an amphoteric surfactant, its preparation method, and its application. Background Technology

[0002] Enhanced oil recovery (EOR) involves injecting additional substances into oil-bearing reservoirs to recover oil. With the development of oilfields, enhanced oil recovery technologies have been widely applied. The main methods of enhanced oil recovery include chemical flooding, thermal recovery, gas flooding, and microbial flooding. Among these, chemical methods include polymer flooding, surfactant flooding, foam flooding, alkaline flooding, and combined flooding using these chemical substances. Chemical flooding technology has become an important means of improving oil recovery in the oilfield industry in recent years.

[0003] my country possesses abundant low-permeability oil reservoirs, which account for approximately one-third of its total crude oil production. Currently, the primary development method for low-permeability reservoirs is water injection, which replenishes formation energy to achieve high and stable production. However, due to their typically deep burial depth and low porosity and permeability, water injection can easily damage the formation, leading to increased injection pressure and decreased injection volume, severely impacting the development effectiveness. Therefore, pressure reduction and injection enhancement measures are necessary. These measures for water injection wells in low-permeability reservoirs mainly include acidizing to remove blockages, nanoparticle unblocking, bio-enzyme unblocking, and surfactant unblocking. Surfactant-based pressure reduction and injection enhancement technology can reduce the seepage resistance of injected water by lowering the oil-water interfacial tension and altering the wettability of the rock surface, thereby increasing the injection volume. It offers advantages such as simple construction, low cost, and good pressure reduction and injection enhancement effects.

[0004] Existing technologies disclose the use of surfactant-activated water flooding and nanoparticle / surfactant composition systems as depressurization and injection enhancement systems. For example, patent CN102965091A discloses a surfactant composition for depressurization and injection enhancement in ultra-low permeability reservoirs. This depressurization and injection enhancement surfactant compound composition comprises a gemini cationic surfactant, a nonionic surfactant (lauric acid diethanolamide), an organophosphonic acid scale inhibitor, an iron ion stabilizer (a compound of hydroxycarboxylic acid and aminocarboxylic acid), and water. The depressurization and injection enhancement composition achieves an interfacial tension of up to 10 at a reservoir temperature of 65°C. -3 With a strength on the order of mN / m and an anti-swelling rate of up to 80%, indoor evaluation results show that the injection pressure can be reduced from 1.4 MPa to 0.92 MPa. Patent CN105154051A discloses a pressure-reducing and injection-enhancing surfactant composition containing an amphoteric surfactant (C... 12 ~C 18The composition comprises alkylamidopropyl hydroxysulfonyl betaine, a clay stabilizer (a copolymer of epichlorohydrin and dimethylamine), a water-soluble polymer scale inhibitor (a copolymer of maleic anhydride and acrylic acid), and water. This pressure-reducing and injection-enhancing composition can be used in ultra-low permeability and extra-low permeability reservoirs with a depth of less than 5 mD. At a reservoir temperature of 53°C, the oil-water interfacial tension can reach 9.4 × 10⁻⁶. -3 The surface area is mN / m, the anti-swelling rate is 60%, and the pressure reduction rate is 15.2%–18.8%. However, existing surfactant-based pressure reduction and injection systems generally have poor temperature and salt resistance, and are not suitable for low-permeability reservoirs with high temperature and high salt content. Therefore, developing a novel temperature- and salt-resistant ionic surfactant for pressure reduction and injection in low-permeability reservoirs is of great significance and has broad application prospects. Summary of the Invention

[0005] The purpose of this invention is to provide an amphoteric surfactant, its preparation method, and its application, in order to solve the technical problems of poor temperature and salt resistance, low pressure reduction rate, and unsatisfactory oil displacement effect of surfactants used for depressurization and injection enhancement in low-permeability reservoirs in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides an amphoteric surfactant with the structure shown in formula (I):

[0008]

[0009] In formula (I), R1 is selected from C4 to C5. 30 Hydrocarbon group; R2 is selected from H, C1-C1. 10 R3 is selected from H, methyl, and ethyl groups; R4 is selected from H and C1-C4 hydrocarbon groups; m1 and m2 are each independently selected from any integer between 0 and 50, and m1+m2=1~50; the structure of R5 is as shown in -(CH2). n1 (CH(OH)) n2 (CH2) n3 SO3(M) n As shown, n1 is selected from any integer between 1 and 4, n2 is selected from 0 or 1, n3 is selected from any integer between 1 and 4, and n1 + n2 + n3 ≤ 6. M includes at least one of alkali metal ions and alkaline earth metal ions. When M is an alkali metal ion, n is 1, and when M is an alkaline earth metal ion, n is 0.5; X i- is an anion, where i is the charge number of the anion.

[0010] The zwitterionic surfactant provided by this invention contains anionic groups (e.g., sulfonic acid groups in R5), cationic groups, and nonionic blocks (e.g., -CH2CH(R3)O-). The synergistic effect of multiple active groups enhances its solubility in water, thereby achieving the purpose of temperature resistance and salt resistance.

[0011] According to some embodiments of the present invention, R1 is selected from C4 to C5. 30 Alkyl, C4-C 30 alkenyl, C6-C 30 Aryl groups.

[0012] According to some embodiments of the present invention, R1 is selected from C4 to C5. 30 Alkyl groups, preferably from C6 to C4. 20 Alkyl groups, more preferably from C8 to C90. 12 alkyl.

[0013] In this invention, R1 is selected from C4 to C5. 30 The hydrocarbon group allows zwitterionic surfactants to be used in low-permeability reservoirs to reduce pressure and enhance injection. More preferably, if R1 is selected from C6 to C6... 20 Alkyl groups, especially C8-C6 12 Alkyl groups can further enhance the depressurization and injection effects of zwitterionic surfactants in low-permeability reservoir oil production.

[0014] According to some embodiments of the present invention, R2 is selected from H, C1 to C2. 10 Alkyl groups, C2-C 10 alkenyl, C6-C 10 Aryl groups.

[0015] According to some embodiments of the present invention, R2 is selected from H, C1 to C2. 10 alkyl.

[0016] According to some embodiments of the present invention, R2 is selected from H and C1-C6 alkyl groups.

[0017] According to some embodiments of the present invention, R4 is selected from H, C1-C4 alkyl, and C2-C4 alkenyl.

[0018] According to some embodiments of the present invention, m1 is selected from any integer between 0 and 35, such as 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 22, 25, 26, 28, 30, 31, 33, 35, etc.

[0019] According to some embodiments of the present invention, m2 is selected from any integer between 0 and 35, such as 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 22, 25, 26, 28, 30, 31, 33, 35, etc.

[0020] According to some embodiments of the present invention, m1+m2 = 2 to 35, for example, it can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 22, 25, 26, 28, 30, 31, 33, 35, etc.

[0021] According to some embodiments of the present invention, m1+m2=2~10.

[0022] In this invention, setting m1+m2 = 1 to 50 allows the use of zwitterionic surfactants in low-permeability reservoir production to reduce pressure and enhance injection. More preferably, if m1+m2 = 2 to 35, especially 2 to 10, the pressure-reducing and injection-enhancing effect of zwitterionic surfactants in low-permeability reservoir production is even better.

[0023] According to some embodiments of the present invention, R5 is selected from -CH2CH2CH2SO3(M). n -CH2CH2SO3(M) n -CH2CH(OH)CH2SO3(M) n .

[0024] According to some embodiments of the present invention, M includes at least one of sodium ions, potassium ions, calcium ions, and magnesium ions.

[0025] In this invention, X i- There are no special restrictions on i. If i is 1, X i- Can be selected from F - Cl - ,Br - I - NO3 - HSO4 - CH3COO - HO-C6H4-COO - CH3-C6H4-SO3 - CH3SO3 - HO-CH2COO - CH3CH(OH)COO - Any one of them; if i is 2, X i- It can be selected from SO4 2-Dicarboxylic acid ions (e.g., oxalate, malonic acid, succinate, glutarate, adipic acid, tartrate, etc.); if i is 3, X i- Citrate can be chosen; if i is 4, X i- One option is to choose tetrabenzoate. Furthermore, X i- In addition to being a simple anion, it can also be a polyanion, such as polyphosphate, polyacrylate, etc.

[0026] In a second aspect, the present invention provides a method for preparing the zwitterionic surfactant described in the first aspect, comprising: reacting an alkylaniline with an epoxy compound, and optionally performing end-capping treatment after the reaction to obtain an alkylaniline polyether; and subjecting the alkylaniline polyether to a quaternization reaction with a quaternizing agent to obtain the zwitterionic surfactant.

[0027] In this invention, the alkylaniline can be purchased directly or prepared in-house. The preparation method can employ existing methods for preparing alkylanilines, for example: nitrating alkylbenzene to obtain alkylnitrobenzene; then hydrogenating the alkylnitrobenzene to obtain alkylaniline.

[0028] According to some embodiments of the present invention, the epoxy compound is selected from C2 to C4 epoxy compounds.

[0029] According to some embodiments of the present invention, the epoxy compound includes at least one of ethylene oxide, propylene oxide, and butane oxide.

[0030] According to some embodiments of the present invention, the capping agent has the structural formula IR', wherein R' is selected from C1 to C4 hydrocarbon groups, preferably from C1 to C4 alkyl groups and C2 to C4 alkenyl groups.

[0031] According to some embodiments of the present invention, the capping agent includes at least one selected from iodomethane, iodoethane, iodopropane, and iodoethylene.

[0032] According to some embodiments of the present invention, the quaternizing agent includes at least one of 3-chloro-2-hydroxypropanesulfonate, 3-bromo-2-hydroxypropanesulfonate, 2-chloro-ethanesulfonate, 2-bromo-ethanesulfonate, 3-chloro-propanesulfonate, and 3-bromo-propanesulfonate.

[0033] According to some embodiments of the present invention, the molar ratio of the epoxy compound to the alkyl aniline is (1-50):1, preferably (2-35):1, and more preferably (2-10):1.

[0034] According to some embodiments of the present invention, the molar ratio of the capping agent to alkylaniline is (0-2.6):1, preferably (1-2.4):1.

[0035] According to some embodiments of the present invention, the molar ratio of the quaternizing agent to alkylaniline is (1-5):1.

[0036] According to some embodiments of the present invention, the reaction conditions for the reaction of the alkylaniline with the epoxy compound include: a reaction temperature of 100-200°C and a reaction pressure of 0-5 MPa.

[0037] According to some embodiments of the present invention, the reaction temperature of the alkylaniline reacting with the epoxy compound is 120–180°C.

[0038] According to some embodiments of the present invention, the reaction pressure of the reaction between the alkylaniline and the epoxy compound is 0.2 to 1 MPa.

[0039] According to some embodiments of the present invention, the reaction of the alkylaniline with the epoxy compound is carried out in the presence of a basic catalyst.

[0040] According to some embodiments of the present invention, the alkaline catalyst includes at least one selected from alkali metals, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal alkoxides, and alkali metal oxides.

[0041] According to some embodiments of the present invention, the amount of alkaline catalyst is 0.1 to 10 wt% of the mass of alkylaniline, preferably 0.5 to 5.0 wt%.

[0042] According to some embodiments of the present invention, the temperature of the quaternization reaction is 20–80°C.

[0043] According to some embodiments of the present invention, the temperature of the quaternization reaction is 60–80°C.

[0044] According to some embodiments of the present invention, the quaternization reaction takes 0.5 to 10 hours.

[0045] According to some embodiments of the present invention, the quaternization reaction takes 5 to 10 hours.

[0046] Thirdly, the present invention provides an oil displacement agent comprising the zwitterionic surfactant described in the first aspect or the zwitterionic surfactant prepared by the preparation method described in the second aspect and water.

[0047] According to some embodiments of the present invention, the mass ratio of the zwitterionic surfactant to water is 1:(50-2000), preferably 1:(80-500).

[0048] In this invention, the water used to prepare the oil displacement agent can be at least one of the following: mineralized water, oilfield injection water, formation water, seawater, rainwater, river water, etc., with a total mineralization range of 0 to 300,000 mg / L, preferably water with a total mineralization range of 1,000 to 50,000 mg / L.

[0049] In addition, to enhance the oil displacement effect, the oil displacement agent provided by the present invention may also include additives commonly used in the art, such as polyether polyols, monoethanolamine, diethanolamine, sodium citrate, EDTA, etc.

[0050] Fourthly, the present invention provides the application of the zwitterionic surfactant described in the first aspect, or the zwitterionic surfactant prepared by the preparation method described in the second aspect, or the oil displacement agent described in the third aspect in oil production, especially in depressurization and enhanced oil production in low-permeability reservoirs.

[0051] The beneficial effects of this invention are at least as follows:

[0052] The zwitterionic surfactant provided by this invention has the advantages of good temperature and salt resistance, high interfacial activity, and the ability to effectively reduce water injection pressure in low-permeability reservoirs. It can be used in enhanced oil production by reducing pressure and increasing injection in low-permeability reservoirs, and can significantly improve the recovery rate of low-permeability reservoirs. Detailed Implementation

[0053] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0054] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0055] Example 1

[0056] 1 mol of nonylaniline and 3 g of sodium hydroxide were added to a reactor equipped with a condenser, a stirrer, and a gas disperser. The mixture was heated to 85°C while passing nitrogen gas through it, and stirred for 1 hour. The vacuum system was then turned on, and the system was evacuated for 1 hour to remove water. The system was then purged with nitrogen gas four times to remove air. The reaction temperature was then adjusted to 140°C, and 2 mol of ethylene oxide was slowly introduced while maintaining a pressure ≤0.5 MPa. After the reaction was completed, the system was purged with nitrogen gas, and 2.1 mol of iodomethane was added. The mixture was reacted at 90°C for 1 hour, cooled, neutralized, and dehydrated to obtain 0.99 mol of nonylaniline polyoxyethylene (2) dimethyl ether.

[0057] 0.99 mol of nonylaniline polyoxyethylene (2) dimethyl ether was dissolved in 500 mL of ethanol and added to a reaction vessel equipped with a condenser, a dropping device and a stirring device. Then 1.1 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added and reacted at 75 °C for 8 h to obtain nonylphenylammonium polyether sulfonate zwitterionic surfactant.

[0058] Example 2

[0059] 1 mol of methylhexadecylaniline and 2.8 g of sodium hydroxide were added to a reactor equipped with a condenser, a stirrer, and a gas disperser. The mixture was heated to 80°C while being purged with nitrogen and stirred for 1 hour. The vacuum system was then activated, and the system was evacuated for 1 hour to remove water. The system was then purged with nitrogen four times to remove air. The reaction temperature was then adjusted to 150°C, and 4 mol of propylene oxide was slowly introduced while maintaining a pressure ≤0.5 MPa. After the reaction was completed, the system was purged with nitrogen, and 2 mol of iodomethane was added. The mixture was reacted at 90°C for 1 hour, cooled, neutralized, and dehydrated to obtain 0.98 mol of methylhexadecylaniline polyoxypropylene (4) dimethyl ether.

[0060] 0.98 mol of methyl hexadecylaniline polyoxypropylene (4) dimethyl ether was dissolved in 1000 mL of ethanol and added to a reaction vessel equipped with a condenser, a dropper and a stirrer. Then 1 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added and reacted at 80 °C for 10 h to obtain methyl hexadecylaniline polyether zwitterionic surfactant.

[0061] Example 3

[0062] 1 mol of octylaniline and 3 g of sodium hydroxide were added to a reactor equipped with a condenser, a stirrer, and a gas disperser. The mixture was heated to 80°C while passing nitrogen gas through it, and stirred for 1 hour. The vacuum system was then turned on, and the system was evacuated for 1 hour to remove water. The system was then purged with nitrogen gas four times to remove air. The reaction temperature was then adjusted to 150°C, and 5 mol of epoxide was slowly introduced while maintaining a pressure ≤0.5 MPa. After the reaction was completed, the system was purged with nitrogen gas, and 2.1 mol of iodoethane was added. The mixture was reacted at 90°C for 2 hours. After cooling, the mixture was neutralized and dehydrated to obtain 0.97 mol of octylaniline polyoxybutylene (5) diethyl ether.

[0063] 0.97 mol of octylaniline polyoxybutylene (5) diethyl ether was dissolved in 1200 mL of ethanol and added to a reaction vessel equipped with a condenser, a dropping device and a stirring device. Then 1.3 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added and reacted at 75 °C for 8 h to obtain octylphenylammonium polyether zwitterionic surfactant.

[0064] Example 4

[0065] 1 mol of dibutylaniline and 4 g of sodium hydroxide were added to a reactor equipped with a condenser, a stirrer, and a gas disperser. The mixture was heated to 80°C while being purged with nitrogen, and stirred for 1 hour. The vacuum system was then activated, and the system was evacuated for 1 hour to remove water. The system was then purged with nitrogen four times to remove air. The reaction temperature was then adjusted to 160°C, and 6 mol of propylene oxide and 6 mol of ethylene oxide were slowly introduced while maintaining a pressure ≤0.5 MPa. After the reaction was completed, the system was purged with nitrogen, and 2 mol of iodomethane was added. The mixture was reacted at 95°C for 2 hours. After cooling, the mixture was neutralized and dehydrated to obtain 0.98 mol of dibutylaniline polyoxyethylene (6)polyoxypropylene (6) dimethyl ether.

[0066] 0.98 mol of dibutylaniline polyoxyethylene (6) polyoxypropylene (6) dimethyl ether was dissolved in 2000 mL of ethanol and added to a reaction vessel equipped with a condenser, a dropper and a stirrer. Then 1.2 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added and reacted at 70 °C for 10 h to obtain dibutylphenylammonium polyether zwitterionic surfactant.

[0067] Example 5

[0068] 1 mol of triacontanilide and 5 g of potassium hydroxide were added to a reactor equipped with a condenser, a stirrer, and a gas disperser. The mixture was heated to 80°C while being purged with nitrogen, and stirred for 1 hour. The vacuum system was then activated, and the system was evacuated for 1 hour to remove water. The system was then purged with nitrogen four times to remove air. The reaction temperature was then adjusted to 160°C, and 30 mol of ethylene oxide was slowly introduced while maintaining a pressure ≤0.5 MPa. After the reaction was complete, the system was purged with nitrogen, cooled, neutralized, and dehydrated to obtain 0.99 mol of triacontanilide polyoxyethylene (30) ether.

[0069] 0.99 mol triacontylaniline polyoxyethylene (30) ether was dissolved in 2000 mL of ethanol and added to a reaction vessel equipped with a condenser, a dropper and a stirrer. Then 1.4 mol of sodium 3-chloro-2-hydroxypropanesulfonate was added and reacted at 80 °C for 10 h to obtain triacontylaniline polyether zwitterionic surfactant.

[0070] Example 6

[0071] The surfactant was prepared according to Example 1, except that sodium 3-chloro-2-hydroxypropanesulfonate was replaced with potassium 3-chloro-2-hydroxypropanesulfonate.

[0072] Example 7

[0073] The surfactant was prepared according to Example 1, except that sodium 3-chloro-2-hydroxypropanesulfonate was replaced with potassium 3-bromo-2-hydroxypropanesulfonate.

[0074] Example 8

[0075] The surfactant was prepared according to Example 1, except that sodium 3-chloro-2-hydroxypropanesulfonate was replaced with sodium 2-chloro-ethanesulfonate.

[0076] Example 9

[0077] The surfactant was prepared according to Example 1, except that sodium 3-chloro-2-hydroxypropanesulfonate was replaced with sodium 3-chloro-propanesulfonate.

[0078] Comparative Example 1

[0079] The surfactant was a tea saponin-modified heterogemini surfactant synthesized according to the method of Example 1 in CN202011452946.3.

[0080] Comparative Example 2

[0081] The surfactant is octadecylamidopropylhydroxysulfonate.

[0082] Comparative Example 3

[0083] The surfactant was sodium nonylphenylamine polyoxyethylene (2) dimethyl ether benzenesulfonate synthesized according to the method in CN202010624678.2.

[0084] Performance Evaluation

[0085] The surfactants prepared in the above embodiments and comparative examples were mixed with injection water from Shengli Oilfield (composition shown in Table 1) to obtain oil displacement agents. The composition of the oil displacement agents is shown in Table 2.

[0086] Table 1. Injected Water in Shengli Oilfield

[0087]

[0088] Table 2 Composition of Oil Displacement Agent

[0089]

[0090]

[0091] The above-mentioned oil displacement agent was used to test its anti-swelling performance, pressure reduction and injection performance, and oil displacement performance. The results are shown in Table 3.

[0092] The testing method is as follows:

[0093] (1) Anti-swelling performance:

[0094] Weigh 0.5g of core powder and 10mL of oil displacement agent into a centrifuge tube, stir well, let stand for 2 hours, and centrifuge at room temperature for 15 minutes (5000 r / min) to obtain the expansion volume V1 of the core powder. Repeat the above steps with 10mL of water and 10mL of kerosene respectively to measure the expansion volumes V2 and V0 of the core powder in water and kerosene. Calculate the anti-swelling rate according to the following formula:

[0095]

[0096] B: Anti-expansion rate, %

[0097] V0: Volume of core powder expanding in kerosene, mL;

[0098] V1: The expansion volume of core powder in the oil displacement agent, mL;

[0099] V2: The volume of core powder expanding in water, in mL.

[0100] (2) Pressure reduction and injection enhancement performance and oil displacement performance

[0101] According to the performance test method of composite oil displacement system in SY / T6424-2000, the physical simulation oil displacement effect test of composite oil displacement system was carried out on a core with a length of 30 cm, a diameter of 2.5 cm, and a permeability of 20 millidarcy. The temperature was 100℃. First, water was used to drive the oil displacement to a water cut of 98 wt%. Then, 0.3 pv (core pore volume) of oil displacement agent was injected and the water cut was driven to 100 wt%. The pressure reduction rate was calculated based on the ratio of the composite oil displacement injection pressure to the water displacement injection pressure. The increase in oil recovery rate was calculated based on the change in the volume of produced crude oil.

[0102] Table 3 Performance evaluation results of oil displacement agents for oil displacement

[0103]

[0104] As can be seen from Table 3, the oil displacement agents in each embodiment are significantly superior to the oil displacement agents in the comparative examples in terms of anti-swelling performance, pressure reduction and injection enhancement performance, and oil displacement performance. Therefore, the zwitterionic surfactant provided by the present invention has good temperature and salt resistance, and its anti-swelling performance, pressure reduction and injection enhancement performance, and oil displacement performance are all superior to existing oil displacement surfactants, making it suitable for enhanced oil production in low-permeability reservoirs through pressure reduction and injection enhancement.

[0105] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An amphoteric surfactant, the structure of which is shown in formula (I): In formula (I), R1 is selected from C4 to C5. 30 Hydrocarbon group; R2 is selected from H, C1-C1. 10 R3 is selected from H, methyl, and ethyl groups; R4 is selected from H and C1-C4 hydrocarbon groups; m1 and m2 are each independently selected from any integer between 0 and 50, and m1+m2=1~50; the structure of R5 is as shown in -(CH2). n1 (CH(OH)) n2 (CH2) n3 SO3(M) n As shown, n1 is selected from any integer between 1 and 4, n2 is selected from 0 or 1, n3 is selected from any integer between 1 and 4, and n1 + n2 + n3 ≤ 6. M includes at least one of alkali metal ions and alkaline earth metal ions. When M is an alkali metal ion, n is 1, and when M is an alkaline earth metal ion, n is 0.5; X i- is an anion, where i is the charge number of the anion.

2. The zwitterionic surfactant according to claim 1, characterized in that, R1 is selected from C4~C 30 Alkyl, C4-C 30 alkenyl, C6-C 30 The aryl group; preferably, R1 is selected from C4 to C5. 30 Alkyl groups, preferably from C6 to C4. 20 Alkyl groups, more preferably from C8 to C90. 12 alkyl; And / or, R2 is selected from H, C1 to C 10 Alkyl groups, C2-C 10 alkenyl, C6-C 10 The aryl group; preferably, R2 is selected from H, C1-C1. 10 Alkyl groups, preferably H-, C1-C6 alkyl groups; And / or, R4 is selected from H, C1-C4 alkyl, C2-C4 alkenyl; And / or, m1 is selected from any integer between 0 and 35; And / or, m2 is selected from any integer between 0 and 35; And / or, m1+m2=2~35, preferably 2~10; And / or, R5 is selected from -CH2CH2CH2SO3(M) n -CH2CH2SO3(M) n -CH2CH(OH)CH2SO3(M) n ; And / or, M includes at least one of sodium ions, potassium ions, calcium ions, and magnesium ions.

3. The method for preparing the zwitterionic surfactant according to claim 1 or 2, characterized in that, include: Alkylaniline is reacted with an epoxy compound, and optionally end-capping is performed after the reaction to obtain alkylaniline polyether; The zwitterionic surfactant is obtained by quaternizing alkyl aniline polyether with a quaternizing agent.

4. The preparation method according to claim 3, characterized in that, The epoxy compound is selected from C2 to C4 epoxy compounds; preferably, the epoxy compound includes at least one of ethylene oxide, propylene oxide, and butane oxide. And / or, the end-capping agent has the structural formula IR', wherein R' is selected from C1-C4 hydrocarbon groups, preferably from C1-C4 alkyl groups and C2-C4 alkenyl groups; preferably, the end-capping agent includes at least one of iodomethane, iodoethane, iodopropane, and vinyl iodide; And / or, the quaternizing agent includes at least one of 3-chloro-2-hydroxypropanesulfonate, 3-bromo-2-hydroxypropanesulfonate, 2-chloro-ethanesulfonate, 2-bromo-ethanesulfonate, 3-chloro-propanesulfonate, and 3-bromo-propanesulfonate.

5. The preparation method according to claim 3 or 4, characterized in that, The molar ratio of the epoxy compound to the alkyl aniline is (1-50):1, preferably (2-35):1, and more preferably (2-10):1; And / or, the molar ratio of the capping agent to alkylaniline is (0–2.6):1, preferably (1–2.4):1; And / or, the molar ratio of the quaternizing agent to alkylaniline is (1-5):

1.

6. The preparation method according to any one of claims 3-5, characterized in that, The reaction conditions for the reaction between the alkylaniline and the epoxy compound include: a reaction temperature of 100–200°C and a reaction pressure of 0–5 MPa.

7. The preparation method according to any one of claims 3-6, characterized in that, The reaction of the alkylaniline with the epoxy compound is carried out in the presence of a basic catalyst; Preferred, The alkaline catalyst includes at least one of alkali metals, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal alkoxides, and alkali metal oxides. And / or, the amount of the alkaline catalyst is 0.1 to 10 wt% of the mass of alkylaniline, preferably 0.5 to 5.0 wt%.

8. The preparation method according to any one of claims 3-7, characterized in that, The quaternization reaction is carried out at a temperature of 20–80 °C.

9. An oil displacement agent comprising the zwitterionic surfactant as described in claim 1 or 2, or the zwitterionic surfactant prepared by any one of claims 3-8, and water; Preferably, the mass ratio of the zwitterionic surfactant to water is 1:(50-2000), more preferably 1:(80-500).

10. The application of the zwitterionic surfactant as described in claim 1 or 2, or the zwitterionic surfactant prepared by any one of claims 3-8, or the oil displacement agent as described in claim 9, in oil production, especially in depressurization and enhanced oil production in low-permeability reservoirs.

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